This invention relates to a mirror array light valve adapted for use with e.g., a cathode-ray tube in conjunction with Schlieren optics forming a system for projecting images upon a display screen. 2. Description of the Prior Art
In forming an image pattern corresponding to a cathode-ray pattern for projection, several techniques are employed. One common technique employs a fluorescent screen containing phosphors which are excited at high energy levels in order to produce an image on the screen. Such a system is employed in commercial television. However, the area of utility for such fluorescent screens is limited, and as the area over which it is desired to project a display becomes larger, other systems must be used.
One such system is the oil film eidophor system, in which an external light source is spatially modulated by an oil film the surface of which is rippled by an electron beam in the cathode-ray tube. The oil eidophor system is very complex, expensive, and subject to cathode deterioration due to the presence of the oil film in the vacuum tube.
An alternative to the eidophor system is to employ an array of deflectable mirror elements in conjunction with an external light source; the mirror elements are deflectable in response to the cathode-ray signal. Such systems are described, for example, in U.S. Pat. No. 2,681,380, issued June 15, 1954, and in IBM Technical Disclosure Bulletin, Volume 13, number 8, August 1970, pages 603-604, both of which describe rectangular edge-mounted mirror elements.
More recently, U.S. Pat. No. 3,746,911, issued July 17, 1973 describes an electrostatically deflectable light valve for use in a large area projection display in which the elements of the array are comprised of a centrally-located post supporting a reflective element, and U.S. Pat. No. 3,886,310, issued May 27, 1975 describes similar electrostatically deflectable light valves in which each element is divided into four wing portions which are oriented so as to be deflectable in four different directions, and which thereby reflect external light to four separate quadrants.